Personality, Pain and the Placebo Effect

A winning personality may do more than help you make friends. According to a new study, people who are selfless and have positive attitudes are more likely to get pain relief from a placebo painkiller than people who are angry or hostile.

Researchers at the University of Michigan say their findings link personality traits with an individual’s susceptibility to the placebo effect from a sham medicine for pain. Personality also affected the amount of a pain relieving chemical released by the brain.

About one-quarter of placebo response was explained by the personality traits of resiliency, straightforwardness, altruism, anger and hostility. Other personality traits didn’t appear to be linked to placebo response.

“We started this study not just looking at measures that might seem more obviously related to placebo responses, such as maybe impulsivity, or reward-seeking, but explored potential associations broadly without a particular hypothesis,” said lead author Dr. Jon-Kar Zubieta, PhD, a member of the Molecular and Behavioral Neuroscience Institute.

“We ended up finding that the greatest influence came from a series of factors related to individual resiliency, the capacity to withstand and overcome stressors and difficult situations. People with those factors had the greatest ability to take environmental information – the placebo – and convert it to a change in biology.”

Zubieta and his team looked at nearly 50 healthy volunteers, both male and female, between the ages of 19 and 38. After a series of tests that identified each individual’s strongest personality trait, the volunteers were hooked up to a brain scanner called a positron emission tomography or PET machine.

They were then told that they were going to experience pain from salt water injected into their jaw muscle, and that a painkiller — actually a placebo — would be injected at certain times.

Patients were asked to rate how much relief they expected to get before the experiment began. Then, as they received the injections, they were asked how well they though the “painkiller” was working.

Researchers used the PET scan to see how much of the natural painkillers called endogenous opioids, were released in certain areas of the brain under painful or “painkiller” conditions. Blood tests were also conducted to measure levels of a stress-induced chemical called cortisol.

Although the cortisol levels did not seem to be influenced by personality or the placebo, the endogenous opioids were activated by the placebo. So were levels of pain relief.

The volunteers who responded most strongly to the placebos rated highly on measures of altruism. They tended to be straightforward, more direct and frank in their approach to others, less guarded and not manipulative.

Zubieta notes that although the findings came from a study involving pain, the results may translate to how personality influences a person’s response to other stress-inducing circumstances.

He believes the findings may also have an influence on the doctor-patient relationship.

For example, patients with certain personality traits might be more likely to work with their doctors and discuss concerns they have about their treatment.

The findings may also help researchers who study new drugs to adjust their results to account for the placebo response of individual volunteers in clinical trials, improving their ability to gauge whether the drug is working.

Because the study followed just a few dozen healthy volunteers, researchers say the experiment must be repeated in larger, more diverse groups for the results to be to be confirmed.